There is known an electronic system including plural electronic units and a containing device accommodating the plural electronic units. A related art is disclosed in Japanese Laid-open Patent Publication No. 2006-216594. The electronic unit includes an electronic part reaching a high temperature. There is known a technique in which air is blown into a housing of the electronic unit in order to assist the electronic part in dissipating heat. Such a housing includes a side plate having air blowing holes.
The housing of the electronic unit is partially reduced, thereby reducing a weight of the electronic unit. However, the reduction might disturb a cooling air blowing into the housing of the electronic unit to reduce the cooling capacity, thereby increasing the temperature of the electronic unit.